1. Field of the Invention
This invention relates to method and apparatus for holding a drilling device in a drill head assembly and, more particularly, to method and apparatus for gripping and engaging a tubular member that has been inserted into the drill head assembly.
2. Description of the Related Art
Drilling devices, such as drill steels, bolt drivers, water distributors, adaptors, and other similar tools, are commonly used in rock drilling operations. It is a conventionally known practice to drill holes in a rock formation by a rotary drill assembly or by a rotary percussion drill assembly. These assemblies include a drill pot that carries a hydraulic motor having a motor shaft rotatably connected to a bevel gear which meshes with another bevel gear rotatably journaled on a support member or hub within the drill housing. The bevel gear is affixed to a rotatable head or cover, which has a seat into which the shank of a drilling device or drill steel is received. A drill bit is positioned on the upper end of the drill steel. With this arrangement, rotation of the motor shaft is transmitted to the drill steel to rotate the drilling device.
A common problem with drill assemblies and other power tools involves obtaining adequate lubrication. Many examples of power tools having improved methods and apparatus for improving lubrication are known in the art. U.S. Pat. Nos. 6,712,157 and 6,871,711 disclose improved power tools having a gear chamber with lubricating grease. The gear chamber is provided with a grease screen that is arranged in close vicinity to the teeth of a bevel gear. The gear chamber covers a substantial part of the teeth to prevent lubricating grease from getting into contact with the bevel gear teeth, which causes viscous friction by the angle drives during tool operation. The gear chamber also includes a grease relocating element that is movably guided along substantially circular paths in housings. The paths are concentrically located with bevel gears and coupling devices.
U.S. Pat. No. 6,109,366 discloses a power tool having a lubricant dispensing device with a receptacle immovably supported in a gear casing. The tool also includes a peripheral side wall and an end wall. The end wall is formed with a through opening for an output shaft and an outlet opening for the lubricant. An agitator element is freely movable within a receptacle for agitating the lubricant by vibratory movements during operation of the tool to facilitate the spreading of the lubricant toward the outlet opening.
U.S. Pat. No. 6,698,533 discloses a powered grinding tool. The tool includes a housing having an angle drive chamber enclosing an angle drive section. The chamber is partially filled with lubricating grease. A rotating drive pinion displaces grease off of gear teeth and deposits the grease along a chamber wall.
Another common problem with drill assemblies relates to the positioning of the drill assembly. Generally, the drill assembly is carried by a self-propelled machine that maneuvers the drill pot into position and in a direction to advance the drill bit into the rock formation. For rock drilling operations in an underground mine, the drill assembly is supported by a boom that is pivotally mounted on the front of a mobile frame. Upward movement of the boom moves the drill steel seated in a drill pot into drilling position. The boom exerts upward pressure on the drill assembly to increase the driving thrust of the drill steel. As a result, the drill steel advances vertically into the rock formation to dislodge rock materials and form an elongated bore in the rock formation to receive a mine roof bolt.
The upward force exerted upon the drill assembly by the boom overcomes resistance of the rock structure to rotation of the drill bit. Such conditions establish the need for drill assembly configurations that increase the amount of torque applied to the drill steel and decrease drill steel slippage. Dust is also a problem that causes deterioration of the gearing and bearings of drill assemblies. Therefore extensive seal arrangements are used on the drill head assemblies.
Many other examples of drill head assemblies and drill heads are known in the art. U.S. Pat. No. 4,294,317 discloses a rotary drill head that is part of a mine roof bolter. The drill head includes a shaft end portion having a deep interior passage adapted to receive the end of a hollow drill bit.
U.S. Pat. No. 5,195,598 discloses a typical drill head assembly for rock drill operations. The drill head assembly includes a rotary drill head having a cover with a flinger that can easily be removed from the drill head assembly. U.S. Pat. No. 3,990,552 discloses a drill head that is part of a rotary percussion drill. U.S. Pat. No. 4,190,116 discloses a rotary drill head that is part of a mine roof bolter.
U.S. Pat. Nos. 5,492,183 and 5,690,183 disclose a drill head unit with a drill chuck. The drill chuck includes a cylindrical central section with steel balls for holding a drill steel in place.
U.S. Pat. No. 5,954,346 discloses a hydraulic chuck having a hydraulic actuator for operating a jaw assembly. The jaw assembly has circumferentially disposed jaws adapted to engage a drill rod. The actuator remains stationary while a spindle rotates. A skirt is attached to the actuator to cover bearing assemblies. The jaws are supported in slots in the spindle. The chuck is secured to a drive unit by bolts received in open slots in an attachment flange to facilitate attachment of the chuck after routine maintenance.
U.S. Pat. Nos. 5,330,013 and 5,492,183 disclose a drill head unit with a drill chuck. The drill chuck includes a cylindrical central section with steel balls for holding a drill steel in place.
U.S. Pat. No. 6,695,071 discloses a drill head for holding a drill steel that includes a drill housing having an internal cavity defined by an upper opening and a lower portion with a lower opening. The internal cavity includes a pair of concentric axially aligned sleeves. An internal sleeve has an inner surface for receiving a drill steel and an outer tapered surface. An external sleeve has an internal tapered mating surface for receiving the internal sleeve. The drill head also includes a sliding member for receiving hydraulic pressure to move the internal sleeve on the tapered surface of the external sleeve into gripping engagement of the drill steel. A Belleville spring provides an opposing force to normally maintain the internal sleeve out of gripping engagement with the drill steel.
Drill assemblies are also used with rock anchors or bonding anchors. A conventional anchor is installed through a five-step process. The first step involves drilling a hole in a rock formation through the use of a conventional drill steel. The second step involves retracting a drill steel from the hole. The third step involves inserting an adhesive cartridge into the hole. The fourth step involves inserting the anchor into the hole. The fifth step involves setting the anchor within the hole.
U.S. Pat. No. 4,413,930 discloses a rock anchor assembly. The rock anchor assembly carries a roof support plate on the opposite end of a bolt. The assembly inserts an anchor into a rock formation. The assembly includes one or more resin cartridges. The cartridges rupture and release resin components for mixing. The assembly rotates the anchor in a preselected direction to mix the resin components before expanding a shell while the resin cures. The cured resin bonds a bolt and expanded shell to the rock formation to resist slippage of the expanded shell and maintain the bolt in tension.
U.S. Pat. No. 7,033,117 discloses a self-drilling rock anchor assembly that is utilized with a drilling assembly. The rock anchor assembly includes an anchor tube, a drill head, an outer thread, a free end and an adapter. The adapter releasably connects with the anchor tube. The adapter also has an inner thread for engaging the outer thread of the anchor tube, a screw stop, and a quick-intervention element. The quick-intervention element connects with a rotatable chuck of a drilling assembly the rock anchor is driven into a rock formation.
U.S. Pat. No. 7,025,538 discloses a rock anchor assembly for use with a drill assembly. The rock anchor assembly includes an anchor tube and an inner tube for holding a resin cartridge. The anchor tube has a drilling head and a trailing end. A drilling machine is coupled for rotary driving of the anchor at the trailing end. The anchor has a centering assembly with a pair of centering elements, which hold the inner tube both radially and axially aligned in the anchor tube.
Another rock anchor assembly, known as the OneStep™ by the Hilti Corporation within the Principality of Liechtenstein, includes an adaptor that allows the anchor to be installed through a two-step process. The first step involves drilling the hole. The second step involves injecting adhesive into the hole to hold the anchor in place.
During drilling operations, the clearance of a drill head assembly is a major concern. Conventional drill head assemblies that are used with the above-described rock anchors typically have a box height of between eight and nine inches (20.3 cm and 22.9 cm). Accordingly, there is a need for an improved drill head assembly that has a reduced height.